Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 0223~300 1998-04-20
The invention relates to a fuel tank for a motor vehicle.
When a fuel tank for a motor vehicle is filled with fuel, fuel
which is already in the tank and which forms a gaseous phase above the
level of the fuel in the tank is displaced by the liquid fuel as it
flows into the tank. In that respect care is to be taken to ensure
that only minimum amounts, if any, of the fuel present in the tank in
the gaseous phase pass into the outside atmosphere. To deal with this
aspect it is nowadays the usual practice for a fuel tank to be
provided with an activated carbon filter (often referred to as the
ACF) through which the gas mixture displaced from the tank by the
rising level of liquid fuel therein flows. When that happens the
hydrocarbons in the gas mixture are at least substantially adsorbed by
the activated carbon of the filter, or another suitable filter
material.
However it is still necessary to reckon on the possibility of
at least a part of the gases which are present above the level of
liquid fuel in the tank being displaced out of the tank through the
filling connection and thus passing into the outside atmosphere. That
is possible whenever the cross-section of the filler pipe is only
incompletely filled with fuel in the filling operation in such a way
that free cross-sectional areas, which are therefore not filled with
fuel, remain in the filler pipe, with gases and vapors thus flowing
through those unfilled cross-sectional regions in opposite
relationship to the direction of flow of the fuel through the filler
pipe into the fuel tank, whereby such gases and vapors can escape into
the atmosphere. Consideration has admittedly already been given to
countering that possibility by the provision in the filler pipe of
sleeves or the like consisting of elastic material, which are intended
to bear sealingly against the outside peripheral surface of the fuel
pump dispensing nozzle assembly and thus close off the cross-section
which is not filled by the latter. It has been found however that this
configuration cannot provide an effective sealing effect in the long
term, not least also having regard to any wear which occurs.
The endeavour has admittedly generally been made to extend the
filler pipe as far as possible into the tank in order to minimise the
spacing between the end of the filler pipe from which the fuel issues
and the bottom of the tank as, at the moment at which that lower end
CA 0223~300 1998-04-20
of the filler pipe is entirely beneath the surface of the liquid fuel
in the tank, the lower opening of the filler pipe is thus closed by
the liquid fuel and accordingly no gases can pass into the filler pipe
at the lower end thereof. In many cases however for practical reasons
it is not possible for the filler pipe to be arranged to terminate so
closely above the bottom of the fuel tank that this would prevent or
at least adequately reduce the flow of gaseous fuel into the filler
pipe through the lower opening thereof. The considerations which make
it seem desirable for the filler pipe not to be arranged to terminate
immediately above the bottom of the tank include the flow resistance
which occurs in the filling operation and which increases with a
decreasing distance between the lower end of the filler pipe and the
oppositely disposed wall portion of the tank, for example therefore
the tank bottom. Furthermore the design of motor vehicle fuel tanks
which in many cases is of an extremely complicated configuration makes
it virtually impossible for the end of the filler pipe to be arranged
at such a short spacing from the tank bottom that the above-indicated
problems would not occur or would occur only to a negligible extent.
In accordance with the present invention there is provided a
20 fuel tank for a motor vehicle, including a filler pipe comprising a
portion which is elastically deformable at least over a part of its
periphery and which is such that in an unexpanded condition it
represents a constriction in the filler pipe.
As will be seen from the description hereinafter of preferred
25 embodiments of the fuel tank according to the invention, the motor
vehicle fuel tank is designed in such a way that the discharge flow of
gas mixture through the filler pipe during a filling operation can be
at least substantially avoided, even when only a small amount of fuel
per unit of time flows through the filler pipe in the filling
30 operation. The fuel tank thus affords a reliable but simple structure
for at least substantially reducing the escape of fuel vapor from the
tank during a tank-filling procedure, wherein the tank can be produced
in a simple and inexpensive manner. Thus the invention is based on the
consideration that, even when a small amount of fuel is flowing
35 through the filler pipe into the tank per unit of time, the cross-
section of the filler pipe is entirely filled with fuel, at least in
the above-mentioned constricted region thereof. Empirical values
CA 0223~300 1998-04-20
indicate that it is readily possible for the magnitude of the cross-
section available for the flow of liquid fuel in the constricted
region of the filler pipe to be so selected that that cross-section is
completely filled, even when only relatively small amounts of fuel are
flowing through the filler pipe per unit of time, whereby the small
amount of fuel flowing through the filler pipe is sufficient to
produce what is referred to as a liquid seal. On the other hand
however that reduced cross-sect:ional region of the filler pipe does
not represent a flow resistance such as to impede the operation of
10 introducing liquid fuel into the tank during the tank-filling
procedure as it is readily possible for the elasticity of the material
defining the constricted cross-sectional region to be so selected that
it automatically expands under the effect of the kinetic energy
involved in the flow of fuel flowing in the filler pipe, more
15 specifically in accordance with the amount of fuel per unit of time,
so that under all circumstances and even in the event of fluctuations
in the feed flow of fuel the invention ensures that the cross-ssection
of the filler pipe is always completely filled with liquid fuel at
least in the portion which is c:onstricted in the non-loaded condition
20 thereof.
Advantageously, at least the portion of the filler pipe which
involves the constricted cross-section is made from plastic material,
while it is also readily possible for the entire filler pipe to be
integrally formed from plastic material.
Embodiments of the present invention will now be described by
way of example with reference to the accompanying drawings in which:
Figure 1 is a diagrammatic view of a fuel tank for a motor
vehicle,
Figure 2 is a side view of a portion of the filler pipe of
30 reduced cross-section,
Figure 3 shows a plan view of the portion illustrated in Figure
2,
Figure 4 is a view in section taken along line IV-IV in Figure
3,
Figure 5 is a view corresponding to Figure 2 of a second
embodiment,
Figure 6 is a view corresponding to Figure 3 of the second
CA 0223~300 1998-04-20
embodiment, and
Figure 7 is a view in section taken along line VII-VII in
Figure 6.
Referring firstly to Figure 1, shown therein is a tank
indicated generally by reference numeral 10 and provided with a filler
pipe 14 which can be closed by means of a cap 12 and which, in the
illustrated embodiment, projects into the internal space or interior
16 of the tank 10 to such an extent that the discharge opening for the
fuel, at the lower end of the filler pipe 14, is disposed in the lower
region of the internal space 16 of the tank 10. It will be noted that
Figure 1 shows the tank in a highly simplified form and in a practical
context the tank may be of a possibly highly complicated
configuration, depending on the respective motor vehicle in which the
tank is to be fitted. That applies in particular if the tank is made
from plastic material, more especially a thermoplastic material.
The tank 10 is also provided at its top side with a venting
connection 20 through which gases and vapors which are to be found in
the tank 10 above the surface of the liquid fuel in the tank can
escape when the tank is being filled. Reference numerals 19 and 20
denote respective possible positions of the surface of the liquid fuel
in the tank.
An activated carbon filter (not shown) can be connected to the
venting connection 20 for very substantially adsorbing the
hydrocarbons and possibly also other substances which may escape from
the tank, thereby to prevent such hydrocarbons and other substances
from passing into the external atmosphere. Reference numeral 22
identifies a removal or drain conduit.
As soon as the surface of the liquid fuel in the tank 10 has
reached a level at which the discharge opening 18 for the fuel is
below the level of the surface of the liquid fuel, as is the case for
example when the liquid fuel in the tank is at the level indicated by
reference numeral 19 in Figure 1, no further gases and vapors can
issue from the tank through the filler pipe 14. Until such a level of
liquid fuel in the tank is reached however, that is to say, for
example at the filling level as indicated by the level 21 in Figure 1,
precautionary steps are to be t:aken in order to prevent fuel vapors
and/or gases from issuing into the external atmosphere through the
CA 0223~300 1998-04-20
filler pipe 14.
For that purpose, in its region which is within the tank 10,
the filler pipe 14 is provided with a portion 24 of reduced diameter
which comprises elastically easily deformable material and which at
each end thereof is connected by way of a respective transitional
region 26 to the respectively adjoining portions indicated at 28 for
example in Figure 2, such portions 28 comprising rigid material.
It will be noted at this point that the terms used above in
relation to the portions 24, 26 and 28 mean that the elastic material
which forms the reduced-diameter portion 24 is on the one hand
sufficiently flexible that, under the influence of the kinetic energy
of the fuel flowing therethrough it can elastically expand, with an
increase in the free cross-section thereof, or it can elastically
contract with a decreasing amount of fuel flowing through the filler
pipe per unit of time, in order thereby to adapt the size of the free
cross-section therein for the flow of fuel therethrough to the
respective amount of fuel per unit of time, whereby the entire cross-
section is filled with liquid fuel. The latter thus forms the above-
mentioned liquid seal, at least in that region which is of variable
cross-section. In this arrangement, the transitional portions 26 are
also made of elastically deformable material. It will be appreciated
that the portions 28 which adjoin the transitional portions 26 and
which have been referred to as rigid may also involve a certain degree
of elastic deformability as is generally usual in relation to plastic
pipes. The use of the term rigid here indicates that deformation does
not occur under the effect of the forces which act on the filler pipe
in normal operation, that is to say also under the effect of the
forces which are to be attributed to the kinetic energy of the liquid
fuel flowing through the filler pipe.
Reference will now be made to Figures 3 and 4 from which it can
be seen in particular that the portion 24 of reduced diameter can be
produced in a simple fashion by the region of the filler pipe 14,
which includes the portion 24, being compressed in order thereby to
produce in the constricted region a substantially elliptical cross-
sectional shape, as can be seen more especially from Figure 4. That
cross-sectional shape occurs when the portion 24 of the filler pipe is
in a non-loaded or unexpanded condition. The free cross-section which
CA 0223~300 1998-04-20
is afforded in that situation can readily be so selected that it
approximately corresponds to the smallest amount of fuel flowing
through the filler pipe per unit of time, that falls to be considered
under practical operating circumstances, for example between 13 and 15
liters per minute. The actual size of the cross-section that must be
afforded for that purpose can be established by simple tests. In the
event of an increase in the amount of fuel flowing through the filler
pipe per unit of time, which with a normal filling rate is at a
maximum between about 50 and 60 liters per minute, the kinetic energy
10 of the flow of fuel produces a corresponding automatic increase in the
size of the cross-section in the portion 24 and possibly also the
adjoining regions 26 so that the entire cross-section in that region
is always completely filled with liquid.
The arrangement of the constricted region 24 in the filler pipe
14 should be so selected that it is sufficiently far away from the end
of the fuel pump dispensing nozzle assembly which is fitted into the
filler pipe 14. That distance is desirably to be so selected that on
the one hand the flow of the jet of fuel into the filler pipe 14
expands the constricted region 24 to such an extent that there is no
build-up of fuel in the filler pipe which can result in automatic
shut-off of the dispensing nozzle assembly, while on the other hand
the jet of fuel is no longer so vigorous that it can open the
constricted region by partially acting thereon, without the liquid
fuel filling the entire cross-section involved. Moreover the
elasticity of the material forming the constricted region 24 is to be
so selected that essentially the kinetic energy of the flowing fuel
causes expansion of the constricted region 24 whose peripheral
dimension does not change.
It will be seen from the foregoing description that the largest
30 possible cross-section corresponds to the lowest level of fuel flow
per unit of time which occurs in practical operation and which is
defined for example in appropriate regulations while the substantially
round cross-section of the filler pipe 14, when the region 24 is in
the condition of being elastically expanded to the maximum amount,
corresponds to the largest amount of fuel flowing per unit of time or
the resulting flow rate.
It will be noted that the filler pipe shown in Figures 2
CA 0223~300 1998-04-20
through 4 can be produced for example by a procedure wherein, in a
continuous extrusion operation, the plastic materials involved, having
different elastic properties, are sequentially extruded in such a way
that a material which is easily elastically deformable after cooling
and hardening is disposed in the constricted region 24 and the
adjoining transitional regions 26 while the respective regions
adjoining same comprise a material which is rigid in the above-
described sense, after cooling and hardening. It is thus readily
possible if necessary for the filler pipe to be produced in one piece
in its entirety. The region 24 of reduced cross-section can be shaped
in a simple manner by the filler pipe being pressed flat in that
region 24 while still in a hot plastic condition so that the region 24
adopts the desired cross-sectional shape. That can be readily
implemented in a controlled and reproducible manner for example when
using supporting air which keeps the interior of the pipe when still
in a hot plastic condition under a slightly increased pressure, for
example in a blow molding mold.
It will be appreciated that it is equally possible for the
filler pipe to be made up from a plurality of portions which are
releasably or fixedly connected together. In that case the portion
which has or forms the constriction in the filler pipe 14 and which is
thus elastically expandable, can be produced in the form of a separate
part whose end regions are adapted to correspond to the cross-section
of the respectively adjoining filler pipe portions, being therefore
normally circular. The stiffness required for connection to the
respectively adjacent pipe portions can be achieved by suitable
dimensioning of the wall thickness or gauge of the pipe portions. It
is however also possible for that portion to be produced by sequential
extrusion, that is to say by extruding materials involving different
properties one after the other.
The portion of the filler pipe 14 which in the illustrated
embodiment is disposed in the internal space 16 of the tank 10 is
surrounded by a tubular holder 30 which can also be in the form of a
grid or of a similar configuration and which is of an inside diameter
that is larger than the outside diameter of the filler pipe 14 in the
non-constricted region thereof. The holder 30 is intended to prevent
the filler pipe 14 bending or buckling sharply downwardly under the
CA 0223~300 1998-04-20
effect of its own weight, in the elastic portion 24, in such a way
that the cross-section of the filler pipe at that location would be
closed or deformed in such a fashion that satisfactory operation of
the filler pipe and more specifically the constricted portion 24
thereof would no longer be ensured. For that purpose it may be
advantageous to provide supports 25 which extend radially or in some
other suitable fashion and which are disposed between the holder 30
and the rigid portion 28 which downwardly adjoins the constricted
portion 24. Instead of individual supports 25 it is also possible to
use an annular grid or lattice or the like as a support element.
Reference will now be made to Figures 5 through 7 showing a
further embodiment in which parts that are the same as those of the
embodiment described hereinbefore with reference to Figures 1 through
4 are denoted by the same references but increased by 100. The
foregoing description of the embodiment of Figures 1 through 4 will
therefore be borne in mind when considering this further embodiment of
the invention.
The difference of substance between the two embodiments
described herein is that, in the embodiment shown in Figures 5 through
7, the actual filler pipe 114 is rigid in its constricted portion 124
but is provided with first and second mutually oppositely disposed
openings 132 which are therefore arranged in displaced relationship
through 180~ in the peripheral direction of the filler pipe. As can be
seen in particular from Figure 6 the openings 132 are of a
substantially elliptical configuration in plan view. The major axis of
the ellipse extends in the longitudinal direction of the filler pipe
114. The configuration afforded by the provision of the openings 132
can also be defined in such terms that, of the peripheral portion of
the filler pipe 114, first and second mutually oppositely disposed
limbs 134 remain in the region of the openings 132; the limbs 134
extend progressively increasing in width in both directions from a
respective plane which extends transversely with respect to the
longitudinal axis of the filler pipe and which extends along the minor
axis of the ellipse in which the limbs 134 are each of their smallest
width, until at the respective axial end of the openings 132 the limbs
134 blend into each other in order again to form the complete
peripheral portion of the filler pipe.
CA 0223~300 1998-04-20
The filler pipe 114 is provided in the region of the openings
132 and extending axially somewhat beyond same with a sleeve portion
which is indicated at 136 and which comprises a highly elastic
material, for example polyurethane or silicone plastic material and
which is of a tube-like or hose-like configuration. The inside
diameter of the sleeve portion 136 is smaller in the unexpanded
condition of the sleeve portion 136 than the outside diameter of the
filler pipe 114 on which it is fitted. By virtue of its elastic
deformability the sleeve portion 136 extends in the region of the two
openings 132 along the boundary edges 138 thereof, with the
consequence that the regions of the sleeve portion 136 which cover
over the openings 132 form in the portion 124 a part of the structure
defining the filler pipe 114, while those regions of the sleeve
portion 136, as is readily apparent from Figure 5, are at a smaller
spacing from the longitudinal axis 140 of the filler pipe 114 than the
completely rigid regions 128 of the filler pipe 114, which adjoin the
portion 124, whereby the cross-section of the filler pipe is reduced
at that location. In this embodiment, the magnitude of the smallest
flow cross-section through the filler pipe thus depends on the width
of the limbs 134 in the region of the minor axis 142 of the respective
elliptical openings 132.
The required sealing integrity as between the outer peripheral
surface of the filler pipe 114 and the sleeve portion 136 can be
easily achieved by the sleeve portion 136 being extended sufficiently
far over the adjoining regions 128 of the filler pipe with the
complete wall configuration extending in the peripheral direction
thereof.
Therefore, in the embodiment of Figures 5 through 7, it is not
a part of the actual filler pipe, which is possibly of an integral
construction, that is expanded or contracted in dependence on the
amount of fuel flowing through the filler pipe per unit of time, but
rather it is the sleeve portion 136 which functions in that way.
It will be appreciated that the above-described embodiments of
the invention have been set forth solely by way of example and
illustration of the principles thereof and that various modifications
and alterations may be made therein without thereby departing from the
spirit and scope of the invention.
